The Academy's Evolution Site

The concept of biological evolution is among the most central concepts in biology. The Academies have been active for a long time in helping those interested in science understand the theory of evolution and 에볼루션 바카라사이트 how it permeates every area of scientific inquiry.

This site provides a range of sources for teachers, students, and general readers on evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.

Tree of Life

The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is a symbol of love and unity in many cultures. It has many practical applications as well, including providing a framework for understanding the history of species and how they react to changing environmental conditions.

The first attempts to depict the world of biology were built on categorizing organisms based on their metabolic and physical characteristics. These methods rely on the collection of various parts of organisms or short DNA fragments have greatly increased the diversity of a Tree of Life2. These trees are mostly populated of eukaryotes, while bacterial diversity is vastly underrepresented3,4.

Genetic techniques have greatly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. We can construct trees by using molecular methods like the small-subunit ribosomal gene.

Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is particularly true for microorganisms that are difficult to cultivate and are typically only represented in a single sample5. A recent analysis of all genomes known to date has produced a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated and whose diversity is poorly understood6.

The expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if certain habitats require protection. This information can be utilized in a variety of ways, including identifying new drugs, combating diseases and improving crops. The information is also valuable to conservation efforts. It can help biologists identify those areas that are most likely contain cryptic species that could have important metabolic functions that could be at risk of anthropogenic changes. While funds to safeguard biodiversity are vital but the most effective way to protect the world's biodiversity is for more people living in developing countries to be empowered with the knowledge to act locally to promote conservation from within.

Phylogeny

A phylogeny, also called an evolutionary tree, illustrates the connections between groups of organisms. Scientists can create an phylogenetic chart which shows the evolutionary relationship of taxonomic categories using molecular information and morphological similarities or differences. Phylogeny plays a crucial role in understanding biodiversity, genetics and evolution.

A basic phylogenetic Tree (see Figure PageIndex 10 Finds the connections between organisms with similar traits and evolved from an ancestor that shared traits. These shared traits are either analogous or homologous. Homologous traits share their evolutionary origins and analogous traits appear similar, but do not share the same ancestors. Scientists group similar traits together into a grouping known as a Clade. All members of a clade share a characteristic, like amniotic egg production. They all derived from an ancestor who had these eggs. A phylogenetic tree is constructed by connecting clades to identify the species who are the closest to one another.

Scientists make use of molecular DNA or RNA data to construct a phylogenetic graph which is more precise and detailed. This information is more precise than morphological information and provides evidence of the evolutionary background of an organism or group. Researchers can use Molecular Data to calculate the evolutionary age of organisms and determine how many organisms have an ancestor common to all.

The phylogenetic relationships of organisms are influenced by many factors, including phenotypic plasticity a kind of behavior that alters in response to specific environmental conditions. This can cause a characteristic to appear more resembling to one species than to another which can obscure the phylogenetic signal. This problem can be addressed by using cladistics. This is a method that incorporates the combination of analogous and homologous features in the tree.

Furthermore, phylogenetics may help predict the length and speed of speciation. This information can assist conservation biologists make decisions about the species they should safeguard from extinction. In the end, it's the conservation of phylogenetic variety which will create an ecosystem that is balanced and complete.

Evolutionary Theory

The fundamental concept in evolution is that organisms change over time as a result of their interactions with their environment. Several theories of evolutionary change have been proposed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed on to the offspring.

In the 1930s and 1940s, theories from a variety of fields -- including genetics, natural selection, and particulate inheritance--came together to form the current evolutionary theory that explains how evolution is triggered by the variations of genes within a population, and how those variations change in time as a result of natural selection. This model, which encompasses mutations, genetic drift as well as gene flow and sexual selection, can be mathematically described.

Recent discoveries in the field of evolutionary developmental biology have revealed that genetic variation can be introduced into a species via mutation, genetic drift, and reshuffling of genes in sexual reproduction, and also through the movement of populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of an individual's genotype over time) can lead to evolution, which is defined by change in the genome of the species over time, and the change in phenotype as time passes (the expression of the genotype in the individual).

Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolutionary. A recent study by Grunspan and colleagues, for example revealed that teaching students about the evidence that supports evolution helped students accept the concept of evolution in a college-level biology class. To learn more about how to teach about evolution, read The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

Traditionally, scientists have studied evolution by looking back--analyzing fossils, comparing species, and observing living organisms. Evolution is not a distant event; it is an ongoing process that continues to be observed today. Bacteria evolve and resist antibiotics, viruses reinvent themselves and escape new drugs, and animals adapt their behavior to the changing climate. The changes that result are often apparent.

It wasn't until the late 1980s that biologists began to realize that natural selection was also in action. The key is that various characteristics result in different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.

In the past, if one allele - the genetic sequence that determines colour was found in a group of organisms that interbred, it could be more common than any other allele. As time passes, that could mean the number of black moths within the population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

It is easier to see evolutionary change when a species, such as bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from one strain. Samples of each population were taken frequently and more than 50,000 generations of E.coli have passed.

Lenski's work has demonstrated that mutations can drastically alter the rate at which a population reproduces--and so, the rate at which it alters. It also demonstrates that evolution takes time, a fact that is hard for some to accept.

Microevolution can be observed in the fact that mosquito genes that confer resistance to pesticides are more common in populations where insecticides have been used. This is because the use of pesticides causes a selective pressure that favors people with resistant genotypes.

The rapidity of evolution has led to a growing appreciation of its importance especially in a planet which is largely shaped by human activities. This includes pollution, climate change, and habitat loss that prevents many species from adapting. Understanding evolution can aid you in making better decisions about the future of the planet and its inhabitants.